Fabrication method for non-volatile memory
Summary by NHIP
Non-volatile memory fabrication
The method forms three doped regions and two gates on a well to create a non-volatile memory transistor. It biases the device to generate a gate current and adjusts capacitances based on whether the voltage difference between the third doped region and the floating gate is smaller or larger than the threshold voltage.
Claim Score by NHIP
Abstract
A fabrication method for a non-volatile memory includes providing a first metal oxide semiconductor (MOS) transistor having a control gate and a second MOS transistor having a source, a drain, and a floating gate. The first MOS transistor and the second MOS transistor are formed on a well. The method further includes biasing the first MOS with a first biasing voltage to actuate the first MOS transistor, biasing the second MOS transistor with a second biasing voltage to enable the second MOS transistor to generate a gate current, and adjusting capacitances between the floating gate of the second MOS transistor and the drain, the source, the control gate, and the well according to voltage difference between the floating gate of the second MOS transistor and the source of the second MOS transistor.

Term
Term ended
Expired 18 June 2023, 3.3 years ago.
- Priority
- Filed
- Granted
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- Today
7 claims: 3 independent, 4 dependent
- 1Broadest claimClaim Score 31, narrow(NHIP)A fabrication method for a metal oxide semiconductor transistor of a non-volatile memory, the method comprising:forming a first doped region, a second doped region and a third doped region on a well;forming a control gate between the first doped region and the second doped region;forming a floating gate between the second doped region and the third doped region;providing a first biasing voltage between the first doped region and the control gate such that the first doped region and the second doped region are conductive;providing a second biasing voltage between the second doped region and the well, so as to generate a channel current between the second doped region and the third doped region, and generate a gate current;wherein if a voltage difference between the third doped region and the floating gate is smaller than a value of a threshold voltage of the metal-oxide-semiconductor transistor, increasing a capacitance between the floating gate and the third doped region to larger than a total capacitance synthesized between the floating gate and the well, the floating gate and the second doped region, and the floating gate and the control gate;or increasing a capacitance between the floating gate and the control gate to larger than a total capacitance synthesized between the floating gate and the third doped region, the floating gate and the well, and the floating gate and the second doped region;wherein if a voltage difference between the third doped region and the floating gate is larger than the threshold voltage, decreasing the capacitance between the floating gate and the third doped region to smaller than the total capacitance synthesized between the floating gate and the well, the floating gate and the second doped region, and the floating gate and the control gate;and decreasing the capacitance between the floating gate and the control gate to smaller than the total capacitance synthesized between the floating gate and the third doped region, the floating gate and the well, and the floating gate and the second doped region.
- 6A fabrication method for metal oxide semiconductor transistors of a non-volatile memory, the method comprising:forming a first doped region, a second doped region and a third doped region on a well;forming a control gate between the first doped region and the second doped region;forming a floating gate between the second doped region and third doped region;providing a first biasing voltage between the first doped region and the control gate such that the first doped region and the second doped region are conductive;providing a second biasing voltage between the second doped region and the well, so as to generate a channel current between the second doped region and the third doped region, and generate a gate current;wherein if a difference between the third doped and the floating gate is smaller than a value of a threshold voltage of the metal-oxide-semiconductor transistor, increasing a capacitance between floating gate and the third doped region to larger than a total capacitance synthesized between the floating gate and the well, the floating gate and the second doped region, and the floating gate and the control gate;or increasing a capacitance between the floating gate and control gate to larger than a total capacitance synthesized between the floating gate and the third doped region, the floating gate and the well and the floating gate and second doped region;wherein the well is an n-well, and the first doped region, the second doped region, and the third doped region are P+ doped region and further comprising providing a P-type substrate;the n-well, the first doped region, the second doped region, and control gate forming PMOS transistor;the n-well, the second doped region, the third doped region, floating gate forming another PMOS transistor.
- 7A fabrication method for metal oxide semiconductor transistors of a non-volatile memory, the method comprising:forming a first doped region, a second doped region and a third doped region on a well;forming a control gate between the first doped region and the second doped region;forming a floating gate between the second doped region and the third doped region;providing a first biasing voltage between the first doped region and the control gate such that the first doped region and the second doped region are conductive;providing a second biasing voltage between the second doped region and the well, so as to generate a channel current between the second doped region and the third doped region, and generate a gate current;wherein if a difference between the third doped and the floating gate is smaller than a value of a threshold voltage of the metal-oxide-semiconductor transistor, increasing a capacitance between floating gate and the third doped region to larger than a total capacitance synthesized between the floating gate and the well, the floating gate and the second doped region, and the floating gate and the control gate;or increasing a capacitance between the floating gate and control gate to larger than a total capacitance synthesized between the floating gate and the third doped region, the floating gate and the well and the floating gate and second doped region;wherein the well a p-well, and the first doped region, the second doped region, and the third doped region are N+ doped region;and further comprising providing a P-type substrate;the p-well, the first doped region, the second doped region, and the control gate forming an NMOS transistor;the p-well, the second doped region, the third doped region, and the floating gate forming another NMOS transistor.
Independent claims3
37 paragraphs in 5 sections, as filed
CROSS REFERENCE TO RELATED APPLICATIONS
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a fabrication method of a single poly one time programmable non-volatile memory (NVM) cell or a single poly multiple time programmable non-volatile memory cell, and more particularly, to a method allowing an increase in speed of data writing by adjusting coupling capacitors of a metal oxide semiconductor transistor in the NVM cell.
2. Description of the Prior Art
In recent years, because NVM devices can maintain data after power-off and are rewritable, they are used to record long-term data. The read/write speed of a NVM is a reference to judge the quality of the NVM.
Referring to FIG. 1, FIG. 1 is a sectional drawing of a non-volatile memory cell <b>10</b> according to the prior art. The NVM cell <b>10</b> includes a first PMOS transistor <b>12</b> and a second PMOS transistor <b>14</b>. The first PMOS transistor <b>12</b> and the second PMOS transistor <b>14</b> are formed on an n-well <b>16</b>. The second PMOS transistor <b>14</b> and the first PMOS transistor <b>12</b> are electrically connected serially to the first PMOS transistor <b>12</b> sharing a second P<sup>+</sup> doped region <b>20</b>. The first PMOS transistor <b>12</b> includes a first P<sup>+</sup> doped region <b>18</b> used to as a drain, and a control gate <b>24</b> made between the first P<sup>+</sup> doped region <b>18</b> and the second P<sup>+</sup> doped region <b>20</b> (a source). The second PMOS transistor <b>14</b> is a floating gate transistor, and includes the drain <b>20</b> (the second P<sup>+</sup> doped region <b>20</b>), a third P<sup>+</sup> doped region <b>22</b> used as a source, a floating gate <b>26</b> made by single layer poly crystal, and a floating gate oxide film <b>32</b> between the floating gate <b>26</b> and the n-well <b>16</b>.
Each electrode of the first PMOS transistor <b>12</b> and the second PMOS transistor <b>14</b> in the NVM cell <b>10</b> according to the prior art can be given different voltages to perform different programmable actions (writing data or reading data). For example, referring to FIG. 1, when writing data to the NVM cell <b>10</b>, a bit line voltage V<sub>1</sub>=0V is applied to the P<sup>+</sup> doped region <b>22</b> of the second PMOS transistor <b>14</b>, and a word line voltage V<sub>2</sub>=0V is applied to the control gate <b>24</b>. A well voltage V<sub>3</sub>=5V is applied to n-well <b>16</b> so the floating gate <b>26</b> of the second PMOS transistor <b>14</b> remains in a floating status, and a source line voltage V<sub>1</sub>=5V is applied to the third P<sup>+</sup> doped region <b>18</b> so the source <b>18</b> of the first PMOS transistor <b>14</b> and n-well <b>16</b> have the same electric potential. At this time, a first P-type channel under the control gate <b>24</b> is formed, so that the second P<sup>+</sup> doped region <b>20</b> and the first P<sup>+</sup> doped region <b>18</b> have the same electric potential. Because the floating gate <b>26</b> of the second PMOS transistor <b>14</b> is under a low voltage (for example, 3˜4V) according to capacitive coupling effect, a second P-type channel is opened under the floating gate <b>26</b>. Collision of holes in the second P-type channel generates hot electrons. The hot electrons quickly cross the floating gate oxide film <b>32</b> and are trapped in the floating gate <b>26</b>.
Referring to FIG. 2, FIG. 2 is a graph relating dropout voltage between the floating gate <b>26</b> and the source <b>22</b> of the NVM cell <b>10</b>, and the gate current I flowing in the second P-type channel. Solid lines and dotted lines represent different biasing voltages. As in FIG. 2, when dropout voltage V<sub>fs </sub>is near a threshold voltage V<sub>th</sub>, the gate current I is near the maximum gate current I<sub>max</sub>. The value of the gate current I directly affects speed of writing data (and reading data) to the NVM cell <b>10</b>. When the dropout voltage V<sub>fs </sub>between the floating gate <b>26</b> and the source <b>22</b> of the second PMOS transistor <b>14</b> is larger or smaller than the threshold voltage V<sub>th </sub>of the PMOS transistor <b>14</b>, which causes the gate current I to flow in the second P-type channel at a rate less than the largest gate current I<sub>max</sub>, the speed in the floating gate <b>26</b> of the second PMOS transistor <b>14</b> affects data writing to the NVM cell <b>10</b>. In addition, the value of the threshold voltage V<sub>th </sub>of the maximum gate current I<sub>max </sub>is ranging from 0.5V to 1.5V.
SUMMARY OF INVENTION
It is therefore a primary objective of the claimed invention to provide a fabrication method of a single poly one time programmable non-volatile memory cell or a single poly multiple time programmable non-volatile memory cell to solve the above-mentioned problem.
According to the claimed invention, a fabrication method for a metal oxide semiconductor transistor of a NVM includes forming a first doped region, a second doped region, and a third doped region on a well; forming a control gate between the first doped region and the second doped region; forming a floating gate between the second doped region and the third doped region; providing a first biasing voltage between the first doped region and the control gate such that the first doped region and the second doped region are conductive; providing a second biasing voltage between the second doped region and the well, so as to generate a channel current between the second doped region and the third doped region, and generate a gate current; wherein if a voltage difference between the third doped region and the floating gate is smaller than the threshold voltage of the floating gate device, increasing a capacitance between the floating gate and the third doped region to larger than a total capacitance synthesized between the floating gate and the well, the floating gate and the second doped region, and the floating gate and the control gate; or increasing a capacitance between the floating gate and the control gate to larger than a total capacitance synthesized between the floating gate and the third doped region, the floating gate and the well, and the floating gate and the second doped region; wherein if a voltage difference between the third doped region and the floating gate is larger than the threshold voltage of the floating gate device, decreasing the capacitance between the floating gate and the third doped region to smaller than the total capacitance synthesized between the floating gate and the well, the floating gate and the second doped region, and the floating gate and the control gate; and decreasing the capacitance between the floating gate and the control gate to smaller than the total capacitance synthesized between the floating gate and the third doped region, the floating gate and the well, and the floating gate and the second doped region.
It is an advantage of the claimed invention that a single poly one time programmable non-volatile memory cell or a single poly multiple time programmable non-volatile memory cell fabricated according to the claimed invention method can write data faster than the NVM cell made according to the prior art.
These and other objectives of the claimed invention will not doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a sectional drawing of a NVM cell according to the prior art.
FIG. 2 is a graph relating voltage of a floating gate and gate current in the metal oxide semiconductor transistor of the NVM cell of FIG. <b>1</b>.
FIG. 3 is a sectional drawing of a NVM cell according to the present invention.
FIG. 4 is a flowchart according to the present invention.
FIG. 5A to FIG. 5F are equivalent circuit schematics of the NVM cell according to the present invention after adjusting a coupling capacitor of the second MOS transistor when more floating gate potential is required.
FIG. 6A to FIG. 6F are equivalent circuit schematics of the NVM cell according to the present invention after adjusting a coupling capacitor of the second MOS transistor when more floating gate potential is required.
FIG. 7A to FIG. 7D are equivalent circuit schematics of the NVM cell according to the present invention after adjusting a coupling capacitor of the second MOS transistor when <sub>less </sub>floating gate potential is required.
From FIG. 8A to FIG. 8D are a equivalent circuit schematic of the NVM cell according to the present invention after adjusting a coupling capacitor of the second MOS transistor when less floating gate potential is required.
DETAILED DESCRIPTION
Referring to FIG. 3, FIG. 3 is a sectional view of a NVM cell <b>40</b> according to the present invention. The NVM cell <b>40</b> includes a P-type semiconductor substrate <b>42</b>, a well <b>44</b>, a first doped region <b>46</b>, a second doped region <b>48</b>, a third doped region <b>50</b>, a control gate <b>52</b>, and a floating gate <b>54</b>. The well <b>44</b> is formed on the P-type semiconductor substrate <b>42</b>. The well <b>44</b>, the first doped region <b>46</b>, the second doped region <b>48</b>, and the control gate <b>52</b> form a first MOS transistor <b>56</b>. The well <b>44</b>, the second doped region <b>48</b>, the third doped region <b>50</b>, and the floating gate <b>54</b> form a second MOS transistor <b>58</b>. The process for writing data to NVM cell <b>40</b> according to the present invention is the same as with the NVM cell <b>10</b> according to the prior art.
The well <b>44</b> can be a p-well or an n-well. If the well <b>44</b> is an n-well the first doped region <b>46</b>, the second doped region <b>48</b>, and the third doped region <b>50</b> are P<sup>+</sup> doped regions; the n-well <b>44</b>, the first doped region <b>46</b>, the second doped region <b>48</b>, and the control gate <b>52</b> form a PMOS transistor; and the n-well <b>44</b>, the second doped region <b>48</b>, the third doped region <b>50</b>, and the floating gate <b>54</b> from another PMOS transistor. However, if the well <b>44</b> is a p-well the first doped region <b>46</b>, the second doped region <b>48</b>, and the third doped region <b>50</b> are N<sup>+</sup> doped regions; the p-well <b>44</b>, the first doped region <b>46</b>, the second doped region <b>48</b>, and the control gate <b>52</b> form a NMOS transistor; and the p-well <b>44</b>, the second doped region <b>48</b>, the third doped region <b>50</b>, and the floating gate <b>52</b> form another NMOS transistor.
When the first MOS transistor <b>56</b> of the NVM cell <b>40</b> is conductive and generates a gate current I from the channel hot electron effect of the floating gate <b>54</b> of the second MOS transistor <b>58</b>, the floating gate <b>54</b> of the second MOS transistor <b>58</b> generates a coupling voltage V<sub>f</sub>. The value of the coupling voltage V<sub>f </sub>relates to the voltages of the well <b>44</b>, the second doped region <b>48</b>, the third doped region <b>50</b>, and the control gate, that is V<sub>f</sub>=α<sub>fw</sub>V<sub>w</sub>+α<sub>fs</sub>V<sub>s</sub>+α<sub>fd</sub>V<sub>d</sub>+α<sub>fc</sub>V<sub>c</sub>. V<sub>w </sub>is voltage of the well <b>44</b>, Vs is voltage of the second doped region <b>48</b>, V<sub>d </sub>is voltage of the third doped region <b>50</b>, V<sub>c </sub>is voltage of the control gate <b>52</b>, and α<sub>fw</sub>, α<sub>fs</sub>, α<sub>fd</sub>, α<sub>fc </sub>are coupling ratios. The coupling ratio is a coupling level from each V<sub>w</sub>, V<sub>s</sub>, V<sub>d</sub>, V<sub>c </sub>to V<sub>f</sub>. That is, V<sub>w</sub>, V<sub>s</sub>, V<sub>d</sub>, V<sub>c </sub>is a voltage volume provided to V<sub>f</sub>.
The value of the coupling ratio α<sub>fs </sub>relates to the coupling capacitor that the NVM cell <b>40</b> generates when the NVM cell <b>40</b> is conductive. That is, a coupling ratio α<sub>fs</sub>=C<sub>fd</sub>/(C<sub>fs</sub>+C<sub>fd</sub>+C<sub>fw</sub>+C<sub>fc</sub>). Please refer to FIG. 3, the dotted lines in FIG. 3 represent the coupling capacitor C<sub>fs </sub>generated between the floating gate <b>54</b> and the second doped region <b>48</b>, the coupling capacitor C<sub>fd </sub>generated between the floating gate <b>52</b> and the third doped region <b>50</b>, and the coupling capacitor C<sub>fw </sub>generated between the floating gate <b>54</b> and the control gate <b>52</b>. The absolute value of the threshold voltage V<sub>th </sub>is between 0.5 volt and 1.5 volts.
Generally, the third doped region <b>50</b> of NVM cell <b>40</b> is connected to a bit line BL, and the control gate <b>52</b> of NVM cell <b>40</b> is connected to a word line WL. When data is to be written to the NVM cell <b>40</b>, the bit line BL and word line WL of the NVM cell <b>40</b> are set to a low voltage (for example, voltage of bit line BL is set to 0V and voltage of word line WL is set to 0V), while the source line voltage V<sub>1 </sub>and the well <b>44</b> are set to a high voltage. Because at this time voltage V<sub>d </sub>of the third doped region <b>50</b> and voltage V<sub>c </sub>of the control gate <b>52</b> are smaller than voltage Vs of the second doped region <b>48</b> and voltage V<sub>w </sub>of the well <b>44</b>, if the |Vf−Vs| features a smaller value than the threshold voltage Vth of the floating gate device, the method increases α<sub>fd </sub>or α<sub>fc </sub>to increase |Vf−Vs|. In addition, increments of α<sub>fd </sub>or α<sub>fc </sub>are larger than increments of α<sub>fs </sub>and α<sub>fw </sub>to increase the value of |Vf−Vs|. However, if the floating gate <b>54</b> features a value of |Vf−Vs| that is larger than the threshold voltage V<sub>th</sub>, α<sub>fs </sub>and α<sub>fw </sub>are increased to increase the coupling voltage V<sub>f</sub>, and increments of C<sub>fd </sub>or Cfc are smaller than increments of C<sub>fs </sub>or C<sub>fw </sub>so as to reduce coupling voltage V<sub>f</sub>.
FIG. 4 presents a method of the NVM cell <b>40</b> according to the present invention. A flow chart <b>100</b> of FIG. 4 includes the following steps:
Step <b>102</b>: Start. At this time, the base form of NVM cell <b>40</b> is formed. Two PMOS transistors or two NMOS transistors are formed by general semiconductor processes on the P-type semiconductor base;
Step <b>104</b>: Provide a first bias voltage between the first doped region <b>46</b> and the control gate <b>52</b>, the first doped region <b>46</b> and the second doped region <b>48</b> becoming conductive (the first bias voltage is larger than the start voltage of the first MOS transistor);
Step <b>106</b>: Provide a second bias voltage between the second doped region <b>48</b> and the well <b>44</b>, generating a channel current between the second doped region <b>48</b> and the third doped region <b>50</b> to generate a gate current I (the magnitude of the second bias voltage is not important if it can generate gate current I of the second MOS transistor, because threshold voltage V<sub>th </sub>does not change with second bias);
Step <b>108</b>: Considering the relationship of dropout voltage and threshold voltage V<sub>th </sub>between the floating gate <b>54</b> and the third doped region <b>50</b>, adjust the layout of the second MOS transistor <b>58</b>. If a voltage difference between the third doped region <b>50</b> and the floating gate <b>54</b> is smaller than the threshold voltage V<sub>th</sub>, increase a capacitance between the floating gate <b>54</b> and the third doped region <b>50</b> to larger than a total capacitance synthesized between the floating gate <b>54</b> and the N-type well <b>44</b>, the floating gate <b>54</b> and the second doped region <b>48</b>, and the floating gate <b>54</b> and the control gate <b>52</b>; or increase a capacitance between the floating gate <b>54</b> and the control gate <b>52</b> to larger than a total capacitance synthesized between the floating gate <b>54</b> and the third doped region <b>50</b>, the floating gate <b>54</b> and the well <b>44</b>, and the floating gate <b>54</b> and the second doped region <b>48</b>. If a voltage difference between the third doped region <b>50</b> and the floating gate <b>54</b> is larger than the threshold voltage V<sub>th</sub>, increase a capacitance between the floating gate <b>54</b> and the third doped region <b>50</b> to smaller than a total capacitance synthesized between the floating gate <b>54</b> and the N-type well <b>44</b>, the floating gate <b>54</b> and the second doped region <b>48</b>, and the floating gate <b>54</b> and control gate <b>52</b>; and increase a capacitance between the floating gate <b>54</b> and the control gate <b>52</b> to smaller than a total capacitance synthesized between the floating gate <b>54</b> and the third doped region <b>50</b>, the floating gate <b>54</b> and the well <b>44</b>, and the floating gate <b>54</b> and the second doped region <b>48</b>;
Step <b>110</b>: End. When NVM cell <b>40</b> is to store data data, the bit line BL or word line WL of the NVM cell <b>40</b> will be set to a high voltage, the first MOS transistor <b>56</b> is conductive, the second transistor <b>58</b> generates the gate current I, the floating gate <b>54</b> of the second MOS transistor <b>58</b> is near the threshold voltage V<sub>th</sub>, and the gate current I is near the maximum gate current I<sub>max</sub>.
Step <b>108</b> can be continually executed until the voltage difference between the floating gate <b>54</b> and the third doped region <b>50</b> becomes suitably close to the threshold voltage V<sub>th</sub>.
Please refer to FIG. 5A to FIG. <b>5</b>F. FIG. 5A to FIG. 5F apply the method according to the present invention when the voltage difference between the floating gate <b>54</b> and the p<sup>+</sup> node <b>48</b> of the second MOS transistor <b>58</b> of the NVM cell <b>40</b> is smaller than the threshold voltage V<sub>th</sub>. Equivalent circuit schematics of the NVM cell <b>40</b> after adjusting the coupling capacitor of the second MOS transistor <b>58</b> of NVM <b>40</b> are presented. The first MOS transistor <b>56</b> and the second MOS transistor <b>58</b> are PMOS transistors, the well <b>44</b> is an N-type well, the control gate <b>52</b> of the first MOS transistor <b>56</b> is electrically connected to the word line WL. C<sub>fd</sub>′ in FIG. 5B is larger than C<sub>fs</sub>′, C<sub>fd</sub>′ in FIG. 5C is larger than C<sub>fw</sub>′, C<sub>fc</sub>′ in FIG. 5E is larger than C<sub>fs</sub>′, and C<sub>fc</sub>′ in FIG. 5F is larger than C<sub>fw</sub>′.
Please refer to FIG. 6A to FIG. <b>6</b>F. FIG. 6A to FIG. 6F apply the method according to the present invention when the voltage difference between the floating gate <b>54</b> and the p<sup>+</sup> node <b>48</b> of the second MOS transistor <b>58</b> of the NVM cell <b>40</b> is smaller than the threshold voltage V<sub>th</sub>. Equivalent circuit schematics of the NVM cell <b>40</b> after adjusting the coupling capacitor of the second MOS transistor <b>58</b> of the NVM <b>40</b> are presented. The first MOS transistor <b>56</b> and the second MOS transistor <b>58</b> are NMOS transistors, the well <b>44</b> is a P-type well, C<sub>fd</sub>′ in FIG. 6B is larger than C<sub>fs</sub>′, C<sub>fd</sub>′ in FIG. 6C is larger than C<sub>fw</sub>′, C<sub>fc</sub>′ in FIG. 6E is larger than C<sub>fs</sub>′, and C<sub>fc</sub>′ in FIG. 6F is larger than C<sub>fw</sub>′.
Please refer to FIG. 7A to FIG. <b>7</b>D. FIG. 7A to FIG. 7D apply the method according to the present invention when the voltage difference between the floating gate <b>54</b> and the p<sup>+</sup> node <b>48</b> of the second MOS transistor <b>58</b> of the NVM cell <b>40</b> is larger than the threshold voltage V<sub>th</sub>. Equivalent circuit schematics of the NVM cell <b>40</b> after adjusting a coupling capacitor of the second MOS transistor of the NVM <b>40</b> are presented. The first MOS transistor <b>56</b> and the second MOS transistor <b>58</b> are PMOS transistors, the well <b>44</b> is a N-type well, the control gate <b>52</b> of the first MOS transistor <b>56</b> is connected to the word line WL, the floating gate <b>54</b> of the second MOS transistor <b>58</b> is connected to the bit line BL. C<sub>fd</sub>′ in FIG. 7C is smaller than C<sub>fs</sub>′ and C<sub>fd</sub>′ in FIG. 7D is smaller than C<sub>fw</sub>′.
Please refer to FIG. 8A to FIG. <b>8</b>D. FIG. 8A to FIG. 8D apply the method according to the present invention when the voltage difference between the floating gate <b>54</b> and the p<sup>+</sup> node <b>48</b> of the second MOS transistor <b>58</b> of the NVM cell <b>40</b> is larger than the threshold voltage V<sub>th</sub>. Equivalent circuit schematics of the NVM cell <b>40</b> after adjusting the coupling capacitor of the second MOS transistor <b>58</b> of the NVM <b>40</b> are presented. The first MOS transistor <b>56</b> and the second MOS transistor <b>58</b> are NMOS transistors, the well <b>44</b> is a P-type well, C<sub>fd</sub>′ in FIG. 8C is smaller than C<sub>fs</sub>′, and C<sub>fd</sub>′ in FIG. 8D is smaller than C<sub>fw</sub>′.
Compared with the method of the NVM cell <b>10</b> according to the prior art, the method of the NVM cell <b>40</b> according to the present invention makes the gate current I of the second MOS transistor <b>58</b> near the largest gate current I<sub>max</sub>, and accordingly, the writing speed of the NVM cell <b>40</b> according to the present invention is faster than the writing speed of the NVM cell <b>10</b> according to the prior art. The method according to the present invention uses well-known semiconductor processes to fabricate the NVM cell <b>40</b>.
Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Contents5
9 sheets
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4 members in 2 offices
Priority claims4
| Document | Office | Kind | Date |
|---|---|---|---|
| 91136578 | Taiwan Province of China | A | |
| 91136578 | Taiwan Province of China | A | |
| 91136578A | – | – | – |
| TW20020136578 | – | – | – |
Members4
| Document | Office | Kind | |
|---|---|---|---|
| TW578271B | Taiwan Province of China | B | |
| US2004121535A1 | United States of America | A1 | |
| TW200411837A | Taiwan Province of China | A | |
| US6812083B2This record | United States of America | B2 |
27 transactions on the USPTO file
Allowed without a rejection on record.
- Non-final rejections
- 0
- Final rejections
- 0
- RCEs
- 0
- Appeals
- 0
Over time
Point at a mark for the transactionTransactions
| Event | Code | |
|---|---|---|
| Recordation of Patent Grant MailedPGM/ | PGM/ | |
| Patent Issue Date Used in PTA CalculationAllowedPTAC | PTAC | |
| Issue Notification MailedAllowedWPIR | WPIR | |
| Receipt into PubsR1021 | R1021 | |
| Dispatch to FDCD1935 | D1935 | |
| Application Is Considered Ready for IssuePILS | PILS | |
| Issue Fee Payment VerifiedN084 | N084 | |
| Issue Fee Payment ReceivedIFEE | IFEE | |
| Receipt into PubsR1021 | R1021 | |
| Mail-Record Petition Decision of Granted Related to AttorneyMP008 | MP008 | |
| Paralegal Petition DecisionPPET | PPET | |
| Receipt into PubsR1021 | R1021 | |
| Workflow - File Sent to ContractorSENT | SENT | |
| Mail Notice of AllowanceAllowedMN/=. | MN/=. | |
| Claims PTOCPTO | CPTO | |
| Notice of Allowance Data Verification CompletedAllowedN/=. | N/=. | |
| Petition EnteredPET. | PET. | |
| IFW TSS Processing by Tech Center CompleteTSSCOMP | TSSCOMP | |
| Case Docketed to Examiner in GAUDOCK | DOCK | |
| Application Return from OIPEWROIPE | WROIPE | |
| Application Is Now CompleteCOMP | COMP | |
| Application Return TO OIPEROIPE | ROIPE | |
| Application Is Now CompleteCOMP | COMP | |
| Application Dispatched from OIPEOIPE | OIPE | |
| Cleared by OIPE CSRL194 | L194 | |
| Request for Foreign Priority (Priority Papers May Be Included)RQPR | RQPR | |
| Initial Exam Team nnIEXX | IEXX |
5 legal events, as the office reported them to INPADOC
Over the term
Point at a mark for the eventEvents
| Event | Code | |
|---|---|---|
| Fee paymentFPAY | FPAY | |
| Fee paymentFPAY | FPAY | |
| Fee paymentFPAY | FPAY | |
| Information on status: patent grantGrantedPATENTED CASESTCF | STCF | |
| AssignmentAS | AS |
Numbers
- Publication, DOCDB
- 6812083
- Publication, EPODOC
- US6812083
- Application
- 10463610
- Application, DOCDB
- 46361003
- Application, EPODOC
- US20030463610
Titles
- English
- Fabrication method for non-volatile memory
Patent term adjustment
- Net adjustment
- 0 days
Classification
- CPC, 5
- G11C16/0408
- H10B69/00
- G11C16/0416
- G11C16/0433
- G11C2216/10
- IPC, 2
- G11C16 04
- H10B69 00
- USPC, 4
- 438205000
- 257E27103
- 438258000
- 438266000